Do You Need to Turn on AC When Using Air Conditioning in Winter?

[EmmettLee]

You don't need to turn on the AC when using air conditioning in winter. The heating system utilizes the car's internal heat cycle, which is a form of waste heat utilization, so there's no need to press the AC button. The functions of car air conditioning are: 1. Achieving cooling effects through the continuous phase change cycle of refrigerant; 2. Removing dust, odors, smoke, and toxic gases from the car's interior air to freshen it, and humidifying the interior air to increase relative humidity. Maintenance methods for car air conditioning include: 1. Don't set the temperature too low; 2. Control the direction of air vents; 3. Avoid prolonged use; 4. Appropriately use high fan speed; 5. Turn off the air conditioning when driving at low speeds.

[MacTalia]

I remember the first time I drove in winter, I turned on the heater without pressing the AC button, and the windows fogged up instantly, making it impossible to see the road. It really scared me. Later, a friend told me that the AC button isn't just for cooling—it also dehumidifies by removing moisture from the car, so even with the heater on, the windows won't fog up. Now, I've gotten into the habit of turning on the AC along with the heater in winter. Although it uses a bit more fuel, safety comes first. Especially on rainy days or when there are more people in the car exhaling moisture, turning on the AC to dehumidify solves the problem. In fact, many new cars with automatic climate control systems manage AC dehumidification automatically, while manual systems just require pressing a button. In short, whether to use AC with the heater in winter depends on whether fogging occurs, but for safety, I recommend keeping the defogging function on all the time.

[AnaMarie]

I've been driving for many years and have the habit of using the heater to warm up in winter without turning on the AC button, because activating the AC for cooling increases engine load and consumes more fuel. Normally, adjusting the temperature knob to a high setting with the heater on is sufficient, and keeping the AC button off saves a bit of money. However, if you encounter window fogging issues, such as on rainy days or when there's a significant temperature and humidity difference inside the car, you must turn on the AC to dehumidify. It's like pressing a button to activate the compressor to absorb moisture, and the fog quickly dissipates. After turning it off, the fog won't reappear immediately. This balanced approach is both safe and economical. I usually observe the severity of the fog first before deciding to turn on the AC to avoid wasting fuel. During regular maintenance, you can also check the air conditioning system to ensure it functions properly, preventing unexpected failures that could increase the risk of fogging.

[DiAdriel]

I've seen too many accidents caused by sudden fogging of car windows in winter, which is really dangerous. The AC button on the air conditioning system actually controls the dehumidification function, specifically designed to dry the air inside the car and prevent fog formation. Therefore, it's best to turn on the AC button when using the heater to utilize its dehumidification capability and ensure clear visibility. If you don't turn it on and rely solely on hot air, it can actually make the humidity worse and cause faster fogging. Especially in cold mornings or when there are many people breathing frequently, I always remind everyone to use the AC for defogging. The operation is very simple: just press the button to keep the interior dry and maintain safe visibility.

[DeclanRose]

From an automotive design perspective, I understand that the AC button's function when using warm air in winter is to activate the compressor for dehumidification to prevent window fogging. The principle is that moisture condenses on the glass to form fog; turning on the AC cooler can extract moisture from the air, making hot air circulation more efficient. Modern vehicles with automatic climate control systems handle this automatically—users only need to set the temperature and fan speed. For manual systems, drivers can toggle the AC button as needed: turn it on when there's fog and off when there's none to avoid unnecessary fuel consumption. I recommend regularly checking the cabin air filter and compressor function to ensure effective dehumidification, enhancing winter driving safety.

[TravisDella]

As an experienced driver, I'm accustomed to only using the heater without pressing the AC button during winter, unless the windows fog up when I activate the dehumidification function. First, I try blowing hot air for a while. If the fog worsens, I press the AC button to dehumidify for a few minutes until the fog disappears, then turn it off. This balances fuel efficiency and safety. Many beginners don't know this operation and blindly turn on AC, which may increase burden, but proper usage can prevent dangers. I also keep a small defogging spray in my car for emergencies, while usually paying attention to the temperature difference inside and outside the car and adjusting promptly.